Material Girl

Carbon black may not be known for high
thermal conductivity, but Researcher Deborah Chung says its high
conformability will help keep products cooler by eliminating air gaps
between electronic components and heat sinks.

Material Engineering Professor Deborah Chung is betting on carbon black in a new thermal paste (patent pending) that she says even outperforms solder.

Present position: Niagara Mohawk Endowed Chair Professor of Materials Research, State University of NY at Buffalo

How you describe your research at cocktail parties: I develop materials for electronic and structural applications.

Describe your new thermal paste: We set out to achieve high conformability with this material, in order to eliminate the air gaps between mating surfaces. Air is a thermal insulator, which creates a high thermal resistance. Our paste consists of polyethylene glycol or butyl ether and carbon black agglomerates that look something like bunches of grapes 30 nm in diameter. Upon compression, these agglomerates flatten out and conform extremely well to the surface topography.

How does it compare to conventional pastes and solders? With this paste, we have achieved a thermal contact conductance of the interface between two copper disks of 3 X 105 W/m2 C, compared to 2 X 105 W/m2 C for a tin-lead antimony solder. The solder is in turn more effective than any of the existing thermal pastes, including those containing graphite, nickel, diamond, and carbon nanotube. The superior thermal performance of our paste is unexpected, due to the relatively low thermal conductivity of carbon black. This paste also does not have some of the inherent disadvantages of solders, such as a tendency to fail or degrade due to fatigue.

What about cost? Carbon black is less expensive than any competing materials.

So you're saying there really is a free lunch? Yes. However, the thermal paste is not an adhesive and does not provide a mechanical bond.

Chung's findings will be published in Carbon Journal in Fall 2003, and she is currently setting up materials transfer agreements with several electronics companies. For more info, contact her atddlchung@eng.buffalo.edu.

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